CN107298895B

CN107298895B - Ink composition for inkjet recording

Info

Publication number: CN107298895B
Application number: CN201610237474.7A
Authority: CN
Inventors: 清本博史; 北胁崇也
Original assignee: Toshiba TEC Corp
Current assignee: Toshiba TEC Corp
Priority date: 2016-04-15
Filing date: 2016-04-15
Publication date: 2020-11-20
Anticipated expiration: 2036-04-15
Also published as: CN107298895A

Abstract

The invention provides an ink composition for ink jet recording, which can form a printing layer with excellent adhesion to an impermeable recording medium by using the ink composition containing a pigment without increasing the workload required for maintenance of an ink jet recording apparatus. The ink composition for inkjet recording of the embodiment contains: a dispersion medium comprising water and a glycol ether having a boiling point of 220 ℃ or higher; a pigment; and core-shell particles comprising a core composed of a hydrophobic acrylic resin and a shell composed of at least one of an aqueous urethane resin and an acrylic-grafted aqueous urethane resin.

Description

Ink composition for inkjet recording

Technical Field

Embodiments of the present invention relate to an ink composition for inkjet recording.

Background

An ink jet recording method is a method of printing by allowing minute droplets of ink to fly and adhere to a recording medium. The method is characterized by being capable of printing high-quality images at high speed with high definition. The inkjet recording method is used in printers for printing plain paper used in offices and industrial printers such as label printers.

In recent years, as inkjet inks for industrial printers, inks using pigment-based colorants instead of dye-based colorants have been increasing. This is because the ink using the pigment has more excellent water resistance and light resistance than the ink using the dye.

Disclosure of Invention

The technical problem to be solved by the present invention is to form a printing layer having excellent adhesion to an impermeable recording medium using an ink composition containing a pigment without requiring much effort in maintenance of an ink jet recording apparatus.

According to an embodiment, an ink composition for inkjet recording contains: the pigment includes a dispersion medium containing water and a glycol ether having a boiling point of 220 ℃ or higher, a pigment, and core-shell particles including a core composed of a hydrophobic acrylic resin and a shell composed of at least one of an aqueous urethane resin and an acrylic-grafted aqueous urethane resin.

Drawings

Fig. 1 is a diagram schematically showing an example of an ink jet recording apparatus which can be used for ink jet recording using the ink composition according to the embodiment.

Description of the symbols

100. Cartridge 101, cartridge

102. Paper feed roller 103, paper feed roller

104. Conveying roller pair 105 and conveying roller pair

106. Registration roller pair 107 and conveyor belt

110. Fan 111 and negative pressure chamber

112. Conveying roller pair 113 and conveying roller pair

114. Conveying roller pair 115Bk, inkjet head

115C, ink jet head 115M, and ink jet head

115Y, ink jet head 116Bk, and ink cartridge

116C, ink cartridge 116M, and ink cartridge

116Y, ink cartridge 117Bk, tube

117C, tube 117M, tube

117Y, tube 118, and sheet discharge tray

P, recording medium.

Detailed Description

Hereinafter, an ink composition for inkjet recording according to an embodiment and a recording method using the same will be described.

Ink composition for ink jet recording

An ink composition for inkjet recording according to an embodiment includes a dispersion medium, a pigment, and core-shell particles. The pigment and the core-shell particles form a suspension or emulsion with the dispersant. The ink composition may further contain an additive such as a pigment dispersant.

The ink composition has a suitable viscosity suitable for ejection from an inkjet recording apparatus, for example, from a print head nozzle of an inkjet printer. For example, the ink composition has a viscosity of 20 mPas or less at 25 ℃.

The components of the ink composition will be described below.

[ pigment ]

The pigment is dispersed in the dispersion medium.

The pigment may be any of inorganic pigments and organic pigments.

Examples of the inorganic pigment include titanium oxide, aluminum pigment, and iron oxide. These inorganic pigments can be used together with carbon black produced by a known method such as a contact method, a furnace method, or a thermal method.

As the organic pigment, for example: azo pigments including azo lake pigments, insoluble azo pigments, azo condensation pigments, and azo chelate pigments; polycyclic pigments such as phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; dye chelates such as basic dye chelates and acidic dye chelates; nitro pigments; a nitroso pigment; or nigrosine.

To obtain a yellow ink composition, pigment yellow 155 is preferably used as the pigment.

As a yellow pigment of the ink composition for inkjet recording, pigment yellow 74 is mainly used. This is because pigment yellow 74 has good color-developing properties and dispersion stability. However, pigment yellow 74 is poor in light resistance. Therefore, a printed matter produced using the ink composition containing pigment yellow 74 is not suitable for outdoor use.

The pigment yellow 155 has good light resistance in addition to sufficient color development and dispersion stability. Therefore, the ink composition containing pigment yellow 155 is particularly suitable for producing printed matter for outdoor use.

Only one pigment may be used. Alternatively, two or more kinds may be used. For example, pigment yellow 155 may be used as the main pigment, and one or more other pigments may be used as the auxiliary pigments. When the auxiliary pigment is used, the color tone can be adjusted.

Self-dispersing pigmenting pigments may be used. The self-dispersible pigment is a pigment which is surface-treated so as to be dispersible in a solvent such as water without a dispersion medium. Here, the surface treatment is, for example, vacuum plasma treatment, diazo coupling treatment, or oxidation treatment. By this surface treatment, at least one functional group such as a carbonyl group, a carboxyl group, a hydroxyl group, and a sulfo group or a salt thereof is bonded to the pigment. For example, the above functional group or a molecule containing a functional group is grafted on the surface of the pigment. In this way, the affinity of the pigment for water is enhanced, and the pigment can be dispersed in a solvent such as water without a dispersant.

When a self-dispersing pigment is used, a pigment dispersant described later may be used together. As described above, the self-dispersible pigment can be dispersed in a dispersion medium such as water without a dispersant. However, when a substance having high hydrophobicity or core-shell particles are present in such a dispersion medium, the particle diameter of the pigment may increase with the passage of time, or the pigment may aggregate and settle. When the self-dispersible pigment and the pigment dispersant are used together, the increase in particle diameter of the pigment and the aggregation and sedimentation of the pigment with the passage of time can be suppressed even if a substance having high hydrophobicity or core-shell particles are present in the dispersion medium.

The average particle size of the pigment is, for example, in the range of 30 to 300nm, more typically in the range of 50 to 200 nm.

The average particle diameter of the pigment can be measured by a particle size distribution meter using a dynamic light scattering method. As the particle size distribution meter, for example, HPPS (Malvern) is available.

The proportion of the pigment in the ink composition is preferably in the range of 2 to 15 mass%, more preferably in the range of 3 to 10 mass%. If the ratio is reduced, it is difficult to achieve a high image density. When the ratio is increased, not only the storage stability of the ink composition may be lowered, but also a problem related to ink ejection may occur.

[ core-Shell particles ]

The core-shell particles are dispersed in a dispersion medium.

The core-shell particles include a core and a shell surrounding the core. The core is composed of a hydrophobic acrylic resin. The shell is composed of at least one of an aqueous urethane resin and an acrylic acid (ester) -grafted aqueous urethane resin.

The core-shell particles function as a fixer. Even when the recording medium is impermeable, the core-shell particles can form a printing layer having good adhesion to the recording medium. Further, the core-shell particles can improve the abrasion resistance of the printed layer.

The proportion of the core-shell particles in the ink composition is preferably in the range of 1 to 40% by mass, more preferably in the range of 1 to 30% by mass, and further preferably in the range of 3 to 20% by mass.

The core-shell particles are present as a dispersed phase of an aqueous resin emulsion having water as a continuous phase, for example, before being mixed with a pigment. The ink composition can be obtained by mixing the aqueous resin emulsion with other components such as a pigment.

[ dispersing Medium ]

The dispersion medium is an aqueous solution comprising water and a glycol ether.

The glycol ethers used herein have a boiling point above 220 ℃. As such glycol ether, for example, diethylene glycol monoisobutyl ether, diethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, or triethylene glycol monobutyl ether can be used.

These glycol ethers are difficult to volatilize due to their high boiling points. These glycol ethers are also excellent in promoting the resolubility of the emulsion or suspension. Therefore, after the ink composition is used, drying of the ink composition in the vicinity of the nozzle of the inkjet head can be suppressed. Therefore, the amount of work required to maintain the inkjet recording apparatus can be reduced.

The proportion of the above glycol ether in the dispersion medium is preferably in the range of 0.5 to 15% by mass, more preferably in the range of 0.5 to 10% by mass, and further preferably in the range of 0.5 to 5% by mass. If the ratio is small, the above effect is also small. If the ratio is increased, the fixing property may be lowered.

(wetting agent)

The dispersion medium may further comprise a humectant to prevent the ink composition from drying. As the wetting agent, a water-soluble liquid wetting agent, for example, a polyhydric alcohol, a nitrogen-containing heterocyclic compound, an amine, or a sulfur-containing compound, can be used. These liquid wetting agents have the effect of improving the dispersion stability of the pigment in the ink composition.

Examples of the polyhydric alcohol include: ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, 1, 5-pentane diol, 1, 6-hexane diol, glycerol, 1,2, 6-hexane triol, 1,2, 4-butane triol, 1,2, 3-butane triol, and 3-methyl-1, 3, 5-pentane triol.

Examples of the nitrogen-containing heterocyclic compound include: n-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1, 3-dimethylimidazolidinone, and-caprolactam.

Examples of amines include: monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, and triethylamine.

Examples of the sulfur-containing compound include: dimethyl sulfoxide, sulfolane, thiodiethanol, and the like.

Examples of the liquid wetting agent other than the polyol, the nitrogen-containing heterocyclic compound, the amine and the sulfur-containing compound include: propylene carbonate, ethylene carbonate, and gamma-butyrolactone.

Among these humectants, glycerin has a high water retention property and a high boiling point as compared with other humectants, and thus is difficult to volatilize. Therefore, glycerin is preferably used as at least a part of the humectant.

The concentration of the humectant in the ink composition is preferably 1 to 40% by mass, more preferably 2 to 40% by mass.

The humectant may be used alone or in combination of two or more. In addition, in order to further improve the wetting effect, the liquid wetting agent may be used together with a solid wetting agent such as urea, thiourea, and ethylene urea. The proportion of the solid humectant in the total humectant is preferably 30% by mass or less.

(pigment dispersant)

The dispersion medium may further contain a pigment dispersant (or a spray stabilizer).

The pigment dispersant is, for example, a polymeric dispersant or a surfactant.

Examples of the polymer dispersant include: polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, acrylic acid-acrylonitrile copolymer, acrylic acid-acrylate copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, and styrene-maleic acid copolymer.

Examples of the surfactant include: and anionic surfactants such as fatty acid salts, higher alkyl dicarboxylic acid salts, higher alcohol sulfate salts, higher alkyl sulfonate salts, condensates of higher fatty acids and amino acids, sulfosuccinate salts, naphthenate salts, liquid fatty oil sulfate salts, alkylallyl sulfonate salts, polyoxyethylene alkyl ether carboxylate salts, polyoxyethylene alkyl ether sulfate salts, and polyoxyethylene alkyl ether phosphate salts.

Nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, and acetylene glycols can also be used as the surfactant.

Among them, polyoxyethylene anionic surfactants such as polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfate salts, and polyoxyethylene alkyl ether phosphate salts are preferable. When such a surfactant is used as a pigment dispersant, the increase in the particle diameter of the pigment with the passage of time, that is, the aggregation and sedimentation of the pigment can be suppressed. Therefore, very excellent storage stability can be achieved.

The amount of the pigment dispersant is preferably in the range of 1 to 50% by mass, more preferably 5 to 40% by mass, relative to the pigment.

(other additives)

The dispersion medium may also contain other additives.

For example, the dispersion medium may further contain a surface tension adjusting agent.

The nonionic surfactant can be used as the surface tension adjuster. Examples of the surface tension adjusting agent include polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, sorbitol alkyl esters, polyoxyethylene sorbitol alkyl esters, and acetylene glycols. Further, as the surface tension adjusting agent, a silicon-based surfactant or a fluorine-based surfactant may be used.

The concentration of the surface tension agent of the ink composition is preferably in the range of 0.5 to 3 mass%.

The dispersion medium may also contain a pH adjuster or a preservative or mildewcide.

Examples of the pH adjuster include: sodium hydroxide, potassium dihydrogen phosphate, and disodium hydrogen phosphate.

Examples of the preservative or antifungal agent include sodium benzoate, sodium pentachlorophenate, sodium 2-mercaptopyridine-1-oxide, sodium sorbate, sodium dehydroacetate, and 1, 2-dibenzoisothiazolin-3-one.

Recording method

For example, an ink jet recording apparatus shown in fig. 1 can be used for ink jet recording using the ink composition.

The inkjet recording apparatus shown in fig. 1 includes a case provided with a paper discharge tray 118. The cassette body is provided with

cassettes

100 and 101,

paper feed rollers

102 and 103, conveying roller pairs 104 and 105, registration roller pair 106, conveying belt 107, fan 110, negative pressure chamber 111, conveying roller pairs 112, 113 and 114, inkjet heads 115C, 115M, 115Y and 115Bk,

ink cartridges

116C, 116M, 116Y and 116Bk, and

tubes

117C, 117M, 117Y and 117 Bk.

The

cartridges

100 and 101 accommodate recording media P different in size. The

paper feed roller

102 or 103 takes out the recording medium P corresponding to the size of the selected recording medium from the

cassette

100 or 101, and conveys it to the conveying

roller pair

104 and 105 and the registration roller pair 106.

The conveying belt 107 is given tension by a driving roller 108 and two driven rollers 109. Holes are provided at predetermined intervals on the surface of the conveyor belt 107. A negative pressure chamber 111 connected to a fan 110 is provided inside the transport belt 107 so that the recording medium P is adsorbed by the transport belt 107. Conveying roller pairs 112, 113, and 114 are provided downstream in the conveying direction of the conveyor belt 107. Further, a heater for heating the printed layer formed on the recording medium P may be provided on the transport path from the transport belt 107 to the paper discharge tray 118.

Above the conveyor belt 107, four rows of ink jet heads that eject ink onto the recording medium P based on image data are arranged. The ink jet head 115C that ejects cyan (C) ink, the ink jet head 115M that ejects magenta (M) ink, the ink jet head 115Y that ejects yellow (Y) ink, and the ink jet head 115Bk that ejects black (Bk) ink are arranged in this order from the upstream.

On the inkjet heads 115C, 115M, 115Y, and 115Bk, there are provided a cyan (C) ink cartridge 116C, a magenta (M) ink cartridge 116M, a yellow (Y) ink cartridge 116Y, and a black (Bk) ink cartridge 116Bk that accommodate the corresponding inks. These

ink cartridges

116C, 116M, 116Y, 116Bk are connected to the inkjet heads 115C, 115M, 115Y, 115Bk through

tubes

117C, 117M, 117Y, 117Bk, respectively.

The ink composition contained in at least one of the

ink cartridges

116C, 116M, 116Y, and 116Bk is the ink composition according to the embodiment. Here, for example, the ink compositions contained in the

ink cartridges

116C, 116M, 116Y, and 116Bk are all assumed to be the ink compositions according to the embodiments.

Next, an image forming operation of the inkjet recording apparatus will be described. First, an image processing unit (not shown) starts performing image processing for recording, and generates control signals that control operations of the various rollers and the negative pressure chamber 111 and the like while generating image signals corresponding to image data.

The

paper feed roller

102 or 103 takes out the recording medium P of the selected size one by one from the

cassette

100 or 101 under control by the image processing unit, and conveys it to the conveying

roller pair

104 and 105 and the registration roller pair 106. The registration roller pair 106 corrects the misalignment of the recording medium P and conveys the recording medium P at a predetermined timing.

The negative pressure chamber 111 sucks air through the holes of the conveyor belt 107. Therefore, the recording medium P is sequentially conveyed to the positions below the inkjet heads 115C, 115M, 115Y, and 115Bk in accordance with the movement of the conveyor belt 107 in a state of being attracted to the conveyor belt 107.

The inkjet heads 115C, 115M, 115Y, and 115Bk eject ink in synchronization with the timing at which the recording medium P is conveyed under the control of the image processing unit. In this way, a color image is formed on a desired position of the recording medium P.

Then, the conveying roller pairs 112, 113, and 114 discharge the recording medium P on which the image is formed to the paper discharge tray 118. When a heater is provided on the conveyance path from the conveyance belt 107 to the paper discharge tray 118, the printed layer formed on the recording medium P can be heated by the heater. By heating with the heater, adhesion of the printing layer to the recording medium P can be improved particularly when the recording medium P is an impermeable medium.

As described above, in this recording apparatus, the ink compositions contained in the

ink cartridges

116C, 116M, 116Y, and 116Bk are all the ink compositions according to the embodiments. Therefore, the printing layer having good adhesion can be formed not only when the recording medium P has permeability similar to that of paper, but also when the recording medium P is impermeable, for example, when the recording medium P has a smooth recording surface made of plastic, glass, or metal. Further, since the ink compositions contained in the

ink cartridges

116C, 116M, 116Y, and 116Bk are the ink compositions according to the embodiments, the ink compositions near the nozzles of the inkjet heads 115C, 115M, 115Y, and 115Bk are less likely to be dried in the recording apparatus. Therefore, the recording apparatus has less burden on maintenance.

[ examples ]

Specific examples are described below.

Preparation of pigment Dispersion

25 parts by mass of a pigment, 5 parts by mass of a surfactant and 70 parts by mass of pure water were mixed, and the mixture was subjected to a dispersion treatment by a bead mill. Here, pigment yellow 155 was used as the pigment, and polyoxyethylene alkyl ether was used as the surfactant. Also, zirconia beads were used as a pulverizing medium of the bead mill.

The beads were then removed from the dispersion and the dispersion was subjected to centrifugation and filtration. Filtration was performed using a 1 μm filter.

As described above, a yellow pigment dispersion liquid having a pigment mass% of 25% was obtained.

Preparation of ink composition

The pigment dispersion was mixed with the other ingredients in the formulation methods shown in tables 1 to 3 below. In tables 1 to 3, the numerical values shown in the right column representing the first column of the component indicate the content (parts by mass) of the component.

Here, as the core-shell particle source, ACRIT (registered trademark) WEN-202UH manufactured by Dainichika chemical Co., Ltd., which is an aqueous resin emulsion, was used. In addition, SURFYNOL (registered trademark) 465 manufactured by Nissan chemical industries, Inc. was used as the ejection stabilizer. Proxel (registered trademark) xL-2 manufactured by Lonza was used as the preservative.

The mixture was stirred for 1 hour using a stirrer, and then filtered through a 1 μm filter. Thus, an ink composition was obtained.

TABLE 1

TABLE 2

TABLE 3

Evaluation of maintainability

Printing was performed by an inkjet recording apparatus using each of the ink compositions shown in tables 1 to 3. Here, an inkjet recording apparatus manufactured by toshiba TEC corporation was used. After printing, the ink jet head was fixed in a position away from the home position and left at a temperature of 25 ℃ for 24 hours. Then, printing was performed again, and the stability of ejection from the inkjet head was checked. Then, the ejection stability was compared with the following criteria, and the maintainability was evaluated. The results are summarized in tables 1 to 3.

Very good: the ejection immediately after the standing was unstable, but the stable ejection was immediately started without a cleaning operation.

O: the ejection was unstable immediately after the standing, but the ejection energy was stable after two or less cleaning operations.

And (delta): the ejection was unstable immediately after the standing, but the ejection was stable after three or more cleaning operations.

X: the ejection was unstable immediately after the standing, and the ejection was unstable after the cleaning operation was repeated.

Evaluation of storage stability

The viscosity and surface tension of the ink compositions were measured for each of the ink compositions shown in tables 1 to 3.

Further, 100cc of each of the ink compositions shown in tables 1 to 3 was measured and put into a sample bottle made of glass. The bottles were sealed and stored in a high-temperature tank set at 50 ℃ for 60 days. Then, the viscosity and surface tension of the ink composition were measured, and the presence or absence of the precipitate was also checked.

Then, these results were compared with the following criteria, and the storage stability was evaluated. The results are shown in tables 1 to 3.

O: almost no physical property change, and no precipitate is precipitated.

And (delta): there was no major change in physical properties or formation of a large amount of precipitates, but there was a minor change in physical properties or formation of a small amount of precipitates.

X: large changes in physical properties occur or a large amount of precipitates are generated.

Evaluation of sealing Property

First, printing was performed using an inkjet recording apparatus using each of the ink compositions shown in tables 1 to 3.

Here, solid printing was performed on a square area of 10mm on one side of the recording medium using an inkjet recording apparatus manufactured by toshiba teger, having a piezoelectric head mounted thereon. The printed layer thus formed was heated for 10 seconds using a blower. At this time, the surface temperature of the recording medium is 50 ℃ or lower.

As the recording medium, an impermeable recording medium made of the following material was used.

Polyvinyl chloride

Polyethylene terephthalate

Stainless steel

Aluminium

Glass

Next, a tape was pasted to the printed layer, and the tape was rubbed with a finger three times. As the adhesive tape, Scotch (registered trademark) repair tape 810 manufactured by sumitomo THREEF corporation was used. Then, the blanket was peeled off, and the state of the printed layer was observed visually. Next, this state was compared with the following standard, and adhesion was evaluated.

O: the pigment was not peeled off from the recording medium at all.

And (delta): a small amount of the pigment was exfoliated from the recording medium.

X: a large amount of the pigment is exfoliated from the recording medium.

The present invention is not limited to the above-described embodiments, and constituent elements can be modified and embodied in the implementation stage without departing from the spirit thereof. Further, various inventions can be formed by appropriate combinations of the plurality of constituent elements disclosed in the above embodiments. For example, some of the components may be deleted from all the components shown in the embodiments. Elements in different embodiments may also be combined as appropriate.

Claims

1. An ink composition for inkjet recording, comprising:

a dispersion medium comprising water and a glycol ether having a boiling point of 220 ℃ or higher;

a pigment; and

core-shell particles comprising a core made of a hydrophobic acrylic resin, and a shell made of at least one of an aqueous urethane resin and an acrylic-grafted aqueous urethane resin,

the proportion of the glycol ether in the ink composition is in the range of 0.5 to 10 mass%,

the glycol ether is tripropylene glycol monomethyl ether,

the dispersion medium further comprises a glycerol, and the dispersion medium,

the ratio of the glycerin in the ink composition is 5% by mass.

2. The ink composition for inkjet recording according to claim 1, wherein the proportion of the core-shell particles in the ink composition is in a range of 1 to 30 mass%.

3. The ink composition for inkjet recording according to claim 2, wherein the proportion of the core-shell particles in the ink composition is in a range of 3 to 20 mass%.

4. The ink composition for inkjet recording according to claim 1 or 2, wherein the proportion of the glycol ether in the ink composition is in a range of 0.5% by mass to 5% by mass.